Endoscopic Ethmoidectomy & Antrostomy: Operative Technique

Anesthesia

Ethmoidectomy and antrostomy can be performed under local or general anesthesia depending on the patient’s wishes, the surgeon’s experience, the health of the patient, and the severity of sinus problems. In all cases, the mucous membranes of nose are anesthetized and vasoconstricted (i.e., to diminish the size of blood vessels) by application of drugs to the nose at the beginning of the operation to minimize blood loss and to improve visualization of the operative field.

Operative Technique

Surgery begins with careful inspection of the nose. Key landmarks are the three turbinate bones or conchae (conchae = shell) arising from the lateral nasal wall and the ostiomeatal complex (a complex where the maxillary, ethmoid and frontal sinuses drain into the side wall of the nose). The most anterior, or nearest to the front structure within the ostiomeatal complex, is the uncinate process. This semilunar (half moon shaped) ridge of bone projects in front of the ostium of the maxillary sinus. Behind or posterior to the uncinate process, is a group of ethmoid cells known as the bulla ethmoidalis. The first step in ethmoidectomy is the careful and atraumatic removal of the uncinate process to visualize the ethmoid sinus and maxillary ostium. In our experience, incomplete removal of the uncinate process is a significant factor in leading to revision surgery. We believe that the uncinate should be removed at its attachment to the lateral nasal wall.

Endoscopic view of right nose showing uncinate process (up) and middle turbinate (mt). Ethmoidectomy begins with probing the space between the uncinate process and bulla ethmoidalis known as the ethmoid infundibulum (infundibulum = funnel-like).

Often complete removal of the uncinate process reveals the natural ostium or drainage pathway of the maxillary sinus into the nose. Various instruments have been designed to enlarge the maxillary ostium and remove the uncinate process. How much to enlarge the natural ostium of the maxillary sinus, also known as an antrostomy (antrostomy = to drain or make a permanent opening in the maxillary sinus to the nose), remains the subject of debate. Some surgeons prefer to only expose the natural ostium, while others routinely remove much of the maxillary sinus wall as part of this step of the procedure. All agree that the antrostomy must include the natural ostium of the sinus because mucocilliary flow is directed to the ostium and mucous may re-enter the sinus through the antrostomy. This so-called “circus effect”, which leads to reinfection of this sinus, is avoided by incorporating the natural ostium in the antrostomy.

Confining maxillary sinus surgery to primarily restoring the drainage pathway of the sinus into the nose is a significant departure from the pre-minimally invasive or functional sinus surgery era. Traditionally, the Caldwell Luc procedure was an integral part of maxillary and ethmoid sinus surgery. However, the American anatomist J. Parsons Schaefer recognized that the “maxillary sinuses are often the cesspool for infectious material from the frontal sinus (sinus frontalis) and certain anterior group of cellulae ethmoidalis” (ethmoid sinus air cells). That is, Schaeffer was implying that the maxillary sinusitis was often the result of infected drainage from the ethmoid and frontal sinuses, and not the cause of infection in these sinuses. In the modern era of sinus surgery, Caldwell Luc is reserved for disease processes such as fracturs or tumors which cannot be treated through an endoscopic transnasal approach.

Endoscopic image of the right nose showing completion of removal of the uncinate process by a debrider exposing the natural ostium of the maxillary sinus (mt = middle turbinate). Following the antrostomy, the maxillary sinus is inspected and polyps, fungus or infected secretion are removed.

An uncommon complication of antrostomy is to injure the nasolacrimal duct (arrows) which drains tears into the nose. When such injuries do occur, the patient may have no problems because the tears drain directly into the nose at the site of injury. Less often the patient experience epiphoria or tears flowing onto the cheek. In such individuals, a dacryocystorhinotomy (DCR) reestablishes the normal drainage into the nose.

Axial cadaver section through the ethmoid sinus. Enlargement outlines the infundibulum (infundibulum = funnel-like) drainage pathway of the ethmoid (yellow) which is bounded anteriorly by the uncinate process (yellow arrow) and posteriorly by the cells of the bulla ethmoidalis. After the uncinate process is removed, ethmoidectomy consist of exenteration of the ethmoid cells. From Schaefer SD et al. The combined anterior-to-posterior and posterior-to-anterior approach to ethmoidectomy: An update. Laryngoscope 116:509-513, 2006.

Exenteration or removal of the cells of the ethmoid sinus has several approaches. Since the 1990’s two separate approaches to the removal of the ethmoid cells have been combined into one procedure. The anterior-to-posterior approach adapted from an earlier technique described by Halle was initially utilized by Professors Walter Messerklinger and Heinz Stammberger. This adaptation began with removal of the uncinate process and antrostomy followed by progressive removal of only diseased ethmoid cells. If indicated, the ethmoidectomy was extended into the posterior ethmoid cells. Sphenoidotomy was performed when the patient had sphenoid sinusitis, mucoceles or tumors of this sinus. The advantage of this technique was that surgery was limited to the diseased sinuses. The disadvantage was that the removal of the superior ethmoid cells required the surgeon to rotate inferiorly their dissection away from the skull base to avoid causing cerebral spinal fluid rhinorrhea (leakage of the fluid surrounding the brain, CSF leak) or injuring the brain.

Sagittal cadaver section through the ethmoid sinus. The anterior-to-posterior approach initially includes removal of the uncinate process and ethmoid cells encompassed by the dotted lines (FR = frontal recess, SS = sphenoid sinus and SER = sphenoethmoid recess). The ethmoid cells above or superior to the dotted lines are exenterated in a retrograde or posterior-to-anterior technique in which the surgical instruments are directed away from the skull base. From Schaefer SD et al. The combined anterior-to-posterior and posterior-to-anterior approach to ethmoidectomy: An update. Laryngoscope 116:509-513, 2006.

The anterior-to-posterior approach was subsequently combined with a posterior-to-anterior adaptation of intranasal sphenoethmoidectomy by Professor Malte Wigand to endoscopes. As originally described, sphenoethmoidectomy began with partial resection of the middle turbinate to expose the anterior or front wall of the sphenoid sinus. The anterior wall of the sphenoid was then removed and the procedure consisted of removing the posterior and then anterior ethmoid cells. This approach permits the surgeon to direct the removal of ethmoid cells away from the skull base and thus lessen the likelihood of injury to this site. The disadvantage of the posterior-to-anterior approach is the extensive nature of the procedure in patients who have minimal sinus disease.

In the combined approach, surgery begins in the anterior nose with removal of the uncinate process and antrostomy. Following antrostomy, the anterior ethmoid cells are removed. Partial or total ethmoidectomy is dictated by the extent of sinus disease. After completing the anterior to posterior dissection, the superior ethmoid cells are removed retrograde under direct endoscopic vision. The ethmoidectomy is completed with visualization of the frontal sinus drainage pathway or frontal recess. This pathway is not disturbed unless the patient has frontal sinusitis and requires a frontal sinusotomy.

Sagittal cadaver section through the ethmoid sinus illustrating retrograde exenteration of the superior ethmoid cells in the combined approach to ethmoidectomy. Enlargement shows the superior ethmoid cells (A) along the skull or roof of the ethmoid sinus prior to their removal. Image B shows removal of the bony partitions between the superior cells with preservation of the skull base. The arrowheads indicate the direction of the surgery which is primarily away from the skull base. From Schaefer SD et al. The combined anterior-to-posterior and posterior-to-anterior approach to ethmoidectomy: An update. Laryngoscope 116:509-513, 2006.